Esophageal subepithelial tumors (SETs) are commonly encountered during screening endoscopy, and leiomyomas are the most common SET of the esophagus. Almost all patients with esophageal leiomyomas are asymptomatic; however, some present with dysphagia, depending on the size of the tumor and the extent to which it encroaches on the lumen. The typical endosonographic features of esophageal leiomyomas include well-demarcated, homogeneously hypoechoic lesions with echogenicity similar to that of the surrounding proper muscle layer, but without cystic changes. Histopathologically, esophageal leiomyomas do not undergo cystic or myxoid degeneration. This report presents a case involving a 65-year-old man with a symptomatic esophageal SET and endosonographic features indicative of malignant neoplasms, who was diagnosed with esophageal leiomyoma with cystic and myxoid degeneration following surgical resection.